PI3K regulates the expression of β-catenin downstream of TCR signalling.

<p>(A) T cells were left untreated or were incubated for 18 hours with the proteasome inhibitor MG132, 20 mM LiCl, plate bound anti-CD3 (10 µg/ml), plate bound anti-CD28 (10 µg/ml), plate bound anti-CD3 plus anti-CD28 (10 µg/ml each). Total cell lysates were used for Western blotting with anti-β-catenin, anti-phospho-β-catenin and anti-GSK3αβ. (B) T cells were stimulated for 18 hours with two different concentrations of plate-bound anti-CD3 in the absence or presence of anti-CD28. Total cell lysates were analysed by Western blot with anti-β-catenin, anti-p-GSK3αβ and anti-tubulin. This experiment was performed twice with similar results. (C) T cells were pre-treated with the PI3K inhibitor Ly294002 (50 µM) or the MEK inhibitor PD98059 (50 µM) for 1 hour prior to 18 hours stimulation with plate bound anti-CD3 in the presence of these inhibitors. Total cell lysates were immunoblotted with indicated antibodies.